Identification of explosives at trace levels by high performance liquid chromatography with a nitrosyl-specific detector

Abstract

A method is presented for the identification and determination of explosives and other related compounds possessing thermally labile nitro or nitroxy groups. It involves the use of high performance liquid chromatography (HPLC) with a nitrosylspecific detector (TEA Analyzer). Results are presented for EGDN (ethanediol dinitrate), NG (glycerol trlnitrate), PETN (2,2-bis( nitroxymethyl)-l,3-propanediol-l,3-dinitrate), Petrin (2-hydroxymethyl-2-nitroxymethyl-l,3-propanediol-l,3-dinitrate), PEDN (2,2-bis( hydroxymethyl)-l,3-propanediol-l,3-dinitrate), RDX (hexahydro-l,3,5-trinitro-s-triazine), NGu (1-nitroguanidine) and HMX (octahydro-l,3,5,7-tetranitro-1,3,5,74etrazocine). Calibration curves covering a concentration range of three orders of magnitude are presented for RDX and PETN. The 90 YO confidence interval for quantiication of RDX is f1.6% at the 4-ng level and that for PETN is f3.2% at the 6-ng level. Retention behavior with silica and NH2-bonded phase HPLC columns is presented. Use of retention times on the two different columns coupled with a response on the nitrosyl-specific detector serves as a convenient method for identification. Although standard explosive preparations were analyzed at nanogram levels without purification, no interferences were presented by ancillary components such as plasticizers and stabilizers.Present techniques for the identification of small aniouiits of explosives usually involve the use of thin-layer chromatography (TLC) (1-3). Some improvements in speed and accuracy are possible through the use of spectrophotometric methods with the TLC techniques (4-6). Despite their widespread use, these techniques possess several disadvantages, including relatively large sample requirements that preclude their use for the analysis of trace quantities of explosive substances (3, 7).Recause of its speed, sensitivity, and simplicity, gas chromatography (GC) has also received attention as a method for the analysis of explosive preparations. This technique, however, is limited by the fact that many explosive compounds are incompatible with the usual GC conditions because of their inherent thermal instability and other problems (8-1 I).Satisfactory results have been obtained only for the analysis of thermally stable nitroaromatic compounds such as the nitro derivatives of toluene (12,13) and such ancillary constituents as plasticizers and stabilizers (9, 11, 14, 25).In an attempt to increase sensitivity and selectivity, GC has been employed with a variety of detectors. Limited success has been achieved using an electron capture detector (EC). However, great care must be taken to avoid overloading or contamination, and special techniques must be used to ensure linearity of response (12, lti, 17).Electron-impact mass spectrometry (MS) seemed to be advantageous for the analysis of explosives a t trace levels; but apart from its denionstrated potential for the identification of nitroarelies (It?), it shows little promise for the analysis of other types of explosives (19-21). Chemical ionization mass s...

Determination of nitroaromatics in biosludges with a gas chromatograph/thermal energy analyzer

“…The TEA has been primarily applied to the analysis of IV-nitrosamines in environmental samples due to the fact that most iV-nitrosamines undergo a stoichiometric reaction to produce nitric oxide (NO) upon pyro-lysis. In addition, TEA responses have been reported for organic nitrites (19), nitrate esters (20), and nitramines (21). However, when analyzed under similar conditions, nitroaromatics produced very weak TEA responses (22).…”

Determination of vasodilators and their metabolites in plasma by liquid chromatography with a nitrosyl-specific detector

“…Figure 1 shows the isocratic separation of each of the nitrate esters from their metabolites, using an NH2 column. Although the separation of nitrate esters of pentaerythritol has been reported previously using a solvent programming technique (18), the present chromatographic conditions represent a more realistic approach to routine analysis of a large number of samples. With this new method, the chromatographic analysis can be completed in approximately 10 min.…”

“…For complex matrices such as blood, plasma, or urine, the detector screens out compounds that do not contain nitrosyl groups, thus simplifying the chromatography and data interpretation. Furthermore, for the nitrate esters, the detector response has been shown to vary linearly with the number of nitrosyl-containing functional groups (18). This feature provides an added advantage over other detectors when quantitating a nitrate ester and its metabolites with a known number of nitrosyl groups, even in the absence of authentic standards.…”

“…For enhanced sensitivity and selectivity, specific detectors have to be used. Lafleur (18) et al recently used a nitrosyl-specific detector, the TEA analyzer, in the identification of explosives at trace levels by interfacing it with high-performance liquid chromatography (HPLC/TEA). Spanggord (19) et al also reported on the application of HPLC/TEA in the determination of nitroglycerin and its metabolites in blood.…”

Recent developments in detection techniques for high-performance liquid chromatography. Part I. Spectroscopic and electrochemical detectors. A review

“…For example, low nanogram levels of some explosives have been identified with this modified catalytic process. 89 The TEA analyser is relatively expensive (ca. E l 5 000) but, provided that some of the problems of linking it up to an HPLC system can be solved, then this detector has considerable potential in certain areas because of its excellent specificity.…”